No discriminatory Top 5s. Don't list things like your top 5 friends, cause someone's feelings will be hurt. A Top 5 should be inclusionary, not exclusionary. Of course, the point is to choose five things over all the others in the world, but I ask you to use your judgement. For example, I'd say posting the Top 5 albums you want to buy next is okay, because it depends more on the mood you're in and what you already own. I'd say posting the Top 5 albums ever is a bad idea, because you're saying those five albums are better than any others, and not just that you happen to like them. But won't you feel silly if you forget one album you really love? It's a bit different from a shopping list. And wow is that a long rule.
It should be stated if a list is real or fantasy. Mixing the two is heavily discouraged, as it changes your motives (and what you can get away with if legality is a question). Two seperate lists should really be made in this instance.
The Top 5 should be interesting and tell us something about yourself. The "Top 5 things to pick up at the grocer's" isn't interesting unless you buy really unorthodox food.
As a corollary to #3, provide a brief rationale (at most a paragraph). No life stories, but we do want to learn about you! Please post it as a comment to the original post, and not as a seperate entry.
If it's an ordinal list, specify! If it's not in any particular order, let us know that, too.